1. Field of the Invention
The present invention is directed to weight sensing methods and apparatus for lifting devices. More particularly, the present invention is directed to weight sensing methods and apparatus that can be retrofit into the frames of existing lifting devices to provide more accurate and more reliable weight sensing.
2. Background of Related Art
Often, when loads are carried by forklifts, it is desirable to measure the amount of weight being carried by the forks. Prior techniques for weight sensing required an indirect calculation of the weight being lifted based on inferences derived from hydraulic pressure or electric current flow. Those techniques are limited in accuracy because such indirect calculations cannot compensate for other factors that affect the amount of electric current flow or hydraulic pressure that are unrelated to the weight on the forks.
Other prior techniques employ the use of strain gauge type force sensors incorporated into the forks, which increases both the complexity and the dimensional bulk of the forks. Those methods are often inaccurate and are often more inaccurate over time as mechanical parts wear and greater force is required to move them. Such prior techniques also often fail over time because the physical contact required with the forks to measure weight with a strain gauge may be lost.
Sensing the weight borne by the forks is important for a forklift operator's safety because preventing forklift overload helps avoid accidents. Moreover, knowing and recording the weights borne by the forklift allows for a better service schedule for the forklift. And, knowing the weight of specific objects borne by the forklift can be useful for inventory purposes.